~ Musings on weather and science

More records to fall? Plus Pressure Cooker Physics!

It looks like another week of dry weather ahead, with a possibility of another record high temperature or two. A sharp ridge of high pressure will keep our skies clear through Thursday before allowing a few clouds in for the weekend, but there is really no reason to think any of said clouds will produce any rain or snow. High temperatures for the next three days will be close to 70 degrees, which will put us near record levels before some cooler air comes in Friday dropping us to the lower 60s followed by the low 50s over the weekend.

We’ve been talking about how the elevation affects cooking. A reader had this question: “Maybe you can explain this to me in a way that makes sense… no one else has been able. Pressure cookers rely on high pressure to generate high heat. Also, when you cover a pot of water, it gets to the boiling point faster, right? So… why doesn’t atmospheric pressure act the same way?”

Actually, it does. A pressure cooker is basically a closed pot that allows the pressure to build up inside as the water tries to boil. A pressure release valve on the top controls how much pressure builds (it’s meant to cook things… not blow up kitchens.) As pressure rises, the boiling point of water rises… up to about 250 degrees instead of 212 degrees for water boiling at standard pressure. It’s just the opposite to what happens when you cook at higher elevations. With lower pressures, water boils at a lower temperature, cooking at a slower rate.

As for putting a lid on a pot to speed up boiling, that’s a little different. Unless the lid is sealed to the pot (not a good idea), its presence only serves to keep the heat inside the pot, which shortens the time needs to get it up to a boil.